Bob Seger was three weeks into his tour when the numb tingle first crept into his hands.

"Whoa, this is weird,” Seger remembers thinking after a Sept. 12 show in Rochester, N.Y.

At 72, the iconic Detroit rocker had been riding high. His 32-show tour was packing arenas, and reviews were glowing. Beyond the nightly set of time-tested heartland hits, Seger and the Silver Bullet Band had been rehearsing all his new songs, prepping for the November release of the album I Knew You When, his emotional tribute to late friend and Eagles co-founder Glenn Frey.

But now his hands were tingling, and the MRI results were startling: Seger had ruptured a disc in his neck. His spinal cord was severely pinched.

That medical evaluation, undisclosed until now, would ultimately lead to an intense spinal surgery, interrupting a tour Seger now hopes to restart in the spring.

“Let’s face it: I’ve been singing real hard for 52 years,” Seger says in his first interview about the situation. “That’s a strain on the upper shoulders and neck. And I guess I finally just popped one out.”

Specialists viewing Seger’s scans were amazed by his lack of pain — “you should be screaming,” one told him — and advised him it was safe to continue performing unless the numbness moved elsewhere.

His remaining 19 dates were called off as he braced for a grueling spinal operation through the back of his neck, guaranteeing an aftermath of severe pain. Less drastic procedures were available, but this one would steer clear of the larynx that had long fueled one of rock’s most distinctive voices.

“I opted for the pain,” Seger says.

Seger underwent his cervical laminectomy Oct. 20 at the University of Michigan hospital, and doctors were pleased with the outcome.

Seger left the hospital four days later facing a tough recovery of at least three months — daily therapy required and no singing allowed. For a week, he could barely walk, calling the pain “about an 8 on a scale of 1 to 10.” Now, heading into Thanksgiving, he’s improving daily and getting around on his own, though a consistent neck pain remains and the only real relief comes with sleep.

'Glenn loved rock 'n' roll'

All things considered, Seger sounds in high spirits, frequently breaking into hearty laughter as he recounts his ordeal and enthuses about the new record.

I Knew You When, released Friday, is Seger’s 18th studio effort, latest in an album catalog that stretches back to 1968’s Ramblin’ Gamblin’ Man,” whose hit title track, fittingly, featured Frey on backing vocals.

Nostalgia courses through the new project, including a black-and-white cover image of a 21-year-old Seger in ’66 — the year he met Frey on the Detroit music scene and forged a lifelong bond as they blossomed from unknowns into household rock names. Inside is a photo of the two backstage at New York’s Madison Square Garden in 2014, Frey’s final visit to a Seger concert.

Conceived soon after Frey’s death in January 2016, "I Knew You When" was initially intended as a personal “boutique project” for Frey’s family, Eagles members and others in the band's tight-knit circle, Seger says.

“In the final analysis, it’s almost as if I’m singing this album to (widow) Cindy Frey and her family,” he says. “That’s the only audience I care about. If they like it, then I’m happy.”

Although the album grew in scope, including covers of songs by the late Lou Reed and Leonard Cohen, every cut was performed with Glenn Frey in mind — "stuff I thought he would like, and stuff I thought Cindy would understand," Seger says.

The album is reflective but hard-charging, filled with more driving guitar and gutsy singing than any Seger release in recent years.

“I wanted this album to rock,” Seger says. “I didn’t want it be some maudlin thing in order to regard his memory. Glenn loved rock ‘n’ roll.”

At the heart of it all is the stirring, midtempo title song, written by Seger two decades ago as a sentimental tribute to rock 'n' roll but dusted off and tweaked to become an homage to his friendship with Frey.

A musical healing

Some may see the album as Seger's grappling with mortality, and in that sense the recent health scare provides a timely backdrop. As much as anything, Seger says, the project was a healing enterprise, an emotional reckoning with the loss of his closest musical friend outside Silver Bullet.

"This really helped," he says. "It made me think about all the things that are important to us. Glenn's family was really important to him, and mine is to me. It gives you perspective."

The fierce rockers include The Highway, celebrating the defiant artistic independence that Seger says he and Frey sought throughout their careers: "I need to turn the wheel / Away from every deal / Until I find out what's real," he sings.

"Glenn always fought the machine," Seger says. "He wanted to push his band in whatever direction he felt it should go, not where the suits thought it should go. And I've had that same problem. I thought that (lyric) said a lot about the struggle that the Eagles and I both went through, trying to be true to ourselves."

Several tracks feature previously recorded instrumentation, including two — Runaway Train and Forward into the Past — plucked from the ‘90s and updated by Seger with engineer-mixer Gerard Smerek at Yessian studios in Farmington Hills. There are five drum credits for the late Little Feat drummer Richie Hayward, who died in 2010, and members of the Silver Bullet Band appear throughout.

Seger is an exuberant autodidact, drawn to nonfiction, and right now he’s devouring Grant” Ron Chernow’s biography of Ulysses S. Grant. (Seger was tickled to learn the U.S. Army general and eventual president was once stationed on Detroit’s Fort Street.) Last Ape Standing, science writer Chip Walter’s 2013 exploration of early hominids, was the inspiration for the new song Gracile and its tale of a lustful early human.

“I thought it would be fun to write a song about a guy 300,000 years ago,” Seger says as he dives into a paleoanthropology tangent, rattling off evolutionary theories, statistics and scientific Latin terms.

There are topical themes too: Runaway Train reflects the ongoing opioid crisis, says Seger, and the Civil War-themed Blue Ridge speaks to modern America’s political and social divide.

And then there are the covers: The acerbic edge in Reed’s Busload of Faith — a song he’d wanted to tackle since hearing it in 1989 — gets an upbeat rock-soul treatment, while Cohen’s Democracy lets him pay homage to an artist he’d admired since ‘67.

Had deadlines permitted, Seger says he also would have covered material by the recently deceased Tom Petty and Gregg Allman.

“There was a bit of poetry in all those artists, and that’s what drew me to them,” Seger says. “Because it’s really special if you can reach that place.”

Also featured is Seger’s own go at a Cohen-esque composition, the waltzing, Spanish guitar-laced Marie.

One potential song that didn’t make the cut was Heartache Tonight, the 1979 Eagles hit he wrote with Frey. Seger joined the Eagles onstage to perform the song at an L.A. memorial for Frey in February 2016, then again at the Kennedy Center Honors and the band’s Classic West concert in July — where 24-year-old Deacon Frey made his debut in his dad's stead.

Seger's guest spots won rave reviews, and people clamored for him to record and tour with his own version of “Heartache Tonight.”

“I think Glenn would be very pleased with this album without me doing it,” Seger says, laughing. “I don’t want to face a lifetime of singing that onstage. It’s hard to sing! It’s at the highest end of my range, really blasting it. Glenn sang the crap out of that.”

On "The Sea Inside," Seger evokes the musical spirit of Led Zeppelin's Kashmir while returning to a familiar lyrical theme: solace in search of inspiration.

"Sometimes you've just got to get away and go deep inside when figuring out what you’re trying to say. I felt like Glenn did that. He suffered for his art. He worked very hard on his lyrics," Seger says. "I know (Don) Henley did that. I did it. The way I do it is I get on a motorcycle and just go for a couple of days.

"That’s the imagery I feel — being out there on the open road, when you just need to be alone and say, ‘OK, here’s where I am now. Where do I want to go?’ ”